Recently, adoption of wear debris sensors in the wind industry has accelerated due to advancements in particle size detection, reduction in cost, and clear value in parallel or in place of traditional vibration systems. Poseidon has installed >5,000 systems in the past three years alone.
At the same time, wind turbine OEMs and gearbox OEMs have developed and started to deploy wind turbine gearboxes with journal/plain bearings in the planet stage in an attempt to reduce failure rates and lower costs. While journal/plain bearings have been around for a long time, their applications have been typically different than the planet stage of wind turbine gearboxes.
This new application of journal/plain bearings on the planet stage has great promise to deliver reliability improvements, but with any new technology deployed in wind: risk is high. Below are a few reasons for why these turbines cannot wait for wear debris:
- Traditional vibration systems aren’t able to monitor journal bearing failures on planetary applications. Without rolling elements, current techniques for planetary fault detection do not work and numerous bearing failures are required to collect data and develop these techniques. Operationally, this is a bad approach for reliability programs; waiting for a potential solution (for an unknown amount of time) fails basic DMFEA standards and principles.
- Alternative traditional condition monitoring techniques are not possible due to bearings located on the planet stage. Techniques such as temperature and proximity probes would need to be wireless due to rotation of the planet section, making them not cost effective or reliable. Further, proximity probes successfully used in fixed speed, torque load only systems using stationary pillow blocks are not viable due to the dynamic load nature of the planet stage of a wind turbine gearbox. These techniques require fixed positioning relative to the fluid film/load zone, which changes as the carrier rotates and because of the dynamic speed/loading caused by wind. Proximity probes typically located in the load zone (see bearing dynamics diagram), which changes in relation to the outer race as the planet carrier rotates. The non-torque loads of a wind turbine gearbox also create too much noise for a proximity probe to be useful in measuring the film breakdown in such a dynamic environment.
- Particle counters are unable to differentiate ferrous vs non-ferrous metals and outside contamination and air bubbles can cause false counting. Particle counters and wear debris sensors are often mistaken. While both are counting debris in the lubricating oil, each has their own advantages and disadvantages. If the goal is monitoring damage of journal bearings within wind, detection of the non-ferrous babbitt material is necessary to detect failure. Because particle counters cannot differentiate between ferrous/non-ferrous/air bubbles/etc., they are not a good solution for monitoring journal bearings within wind. A second issue with particle counters is the low flow rates. Due to the restrictions of flow, only a very small portion of the unfiltered oil passes through the sensor. This significantly reduces the chances of seeing debris from journal bearing failures and the data becomes unreliable.
- Size matters when looking at detection of the non-ferrous babbitt material within wind turbine gearbox applications. An example of this in common wind turbine gearbox designs is clocking/spinning bearings, which produce extremely small debris. Because babbitt layers on journal bearing are thin compared to the steel layer of roller bearings, the debris generated by a journal bearing can be extremely small. Only Poseidon’s DM4500/4600 is able to detect non-ferrous babbitt material as small as 150µm, most other sensors are well above 250µm.
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